安徽绩溪伏岭花岗岩LA-ICP-MS锆石U-Pb年龄的精确测定及其地质意义  

New Dating of the Fuling Granite Body with LA-ICP-MS Zircon U-Pb in Jixi,Anhui Province and Their Geological Significance

作　　者：陈芳[1,2] 王登红[3] 杜建国[3] 许卫[2] 胡海风[2,4] 余有林[2] 汤金来[2] 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]安徽省地质调查院,安徽合肥230001 [3]国土资源部成矿作用与资源评价重点实验室,中国地质科学院矿产资源研究所,北京100037 [4]合肥工业大学资源与环境工程学院,安徽合肥230009

出　　处：《岩矿测试》2013年第6期970-977,共8页Rock and Mineral Analysis

基　　金：中国地质调查局地质矿产远景调查专项“安徽省矿产资源潜力评价”(1212010881616);安徽省公益性地质调查项目“安徽省重要金属成矿区带与邻区成矿地质条件对比研究”(2010-g-14)

摘　　要：伏岭岩体位于安徽省南部钦杭东段北部成矿带,周边已发现很多矿床(点)。为探讨岩体与成矿的关系,本次研究采集了伏岭岩体地表新鲜花岗岩样品两件,通过LA-ICP-MS锆石U-Pb测年技术,获得采于伏岭岩体小昌溪单元的过渡部位的粗粒钾长花岗岩的206Pb/238U加权平均年龄为(129.95±0.70)Ma(n=14),MSWD=1.7,可以代表小昌溪单元的主体成岩年龄;而采于伏岭岩体的饭蒸尖单元边缘的中细粒钾长花岗岩的206Pb/238U加权平均年龄为(133.9±1.1)Ma(n=8),MSWD=1.06,不能代表饭蒸尖单元主体成岩年龄。测试结果与前人野外填图事实相矛盾,这可用岩体由边部向中心逐步冷凝结晶的事实规律得到解释,亦可解释为二者分别代表了岩体的成岩年龄和侵位年龄。伏岭岩体为燕山晚期早阶段(早白垩世)岩浆活动的产物,较前人所得结果老10 Ma左右。本次研究采用的锆石U-Pb同位素测年精度更高,因而更能代表岩体主体形成年龄,研究认为今后有必要开展伏岭岩体与周边矿床(点)成因联系的研究,这对于矿床成因和区域成矿规律的认识具有重要意义。The Fuling rock body is located in the eastern section of the northern part of the Qinhang metallogenic belt in southern Anhui Province.There are many deposits （spots） that have been explored around it.2 fresh granite samples in the surface of Fuling rock body have been collected and the zircons analyzed using LA-ICP-MS method in an attempt to determine the relationship between the rock body and mineralization.The weighted average 206pb/238U ages for zircons from the coarse-grained K-feldspar granite collected in the transition part of the Xiaochangxi unit is （129.95 ±0.70） Ma （n =14）,MSWD =1.7,which indicates the formation age of the main part of the Xiaochangxi unit.The average 206pb/238 U ages for zircons from the middle-fine-grained K-feldspar granite collected in the edge of the Fanzhengjian unit is （133.9 ± 1.1） Ma（n =8）,MSWD =1.06,which is not in agreement with the formation age of the main part of the Fanzhengjian unit.These results contradict with the geological mapping.Either the rocks cooled gradually from the rim inwards,or the two different ages represent the diagenetic age and the emplacement age respectively.The Fuling rock body is the production of magma activity in the early stage of the late Yanshanian Period （early Cretaceous）,which is almost 10 Ma older than previous research results.This dating is more representative of the formation age of the rock body according to the high precision of the Zircon U-Pb technology.

关 键 词：伏岭花岗岩 LA-ICP-MS锆石U-PB测年 早白垩世 

分 类 号：P578.121[天文地球—矿物学] P533[天文地球—地质学]